Height limit trade-offs

November 20, 2012, 10:45 pm

The Cairo. CC image from NCinDC.

Following up on some of the trade-offs mentioned at the end of the previous post on DC’s height act.

In the discussion of Kaid Benfield’s piece supporting DC’s height limit, several comments are worth highlighting. First, Payton Chung notes the need to discuss more than just supply, but to also realize the strength of the demand for living in DC:

I think that a splendid city could be built within the current Height Act, or a revised one, or perhaps even none at all. However, I’ll raise a few counter-factuals, recognizing that I also have not gotten around to writing more extensively about the topic:

1. The growth projections for this region are staggering: +874,394 households and +1,625,205 jobs from 2010-2040. Yet your (and my) preferred strategy of retrofitting mid-rise corridors has a limited upside. Toronto’s Avenues plan, which promotes redeveloping its extensive streetcar commercial strips with a 1:1 street enclosure ratio (building height=street width), only projects an additional 2,000 residents (=1,000 units) per mile of redeveloped “avenue” frontage. Given the District’s small footprint, that’s not going to be enough to absorb very many new residents, much less to increase the city’s housing stock by enough to improve housing affordability.

2. As you well know, a huge difference between Washington and the world’s great mid-rise cities (not just the European capitals, but also cities like Buenos Aires and Kyoto) is that Washington’s mid-rises peter out into single-family houses just one or two miles from the core, while those cities have multifamily-density housing stretching clear to the city limits. This brings me to your point about creativity: what high-rise downtowns do is to concentrate high-value uses within a small area instead of letting it spill out into neighborhoods. High-value office, hotel, and retail uses have priced out most of the creativity in Dupont Circle, Woodley Park, Georgetown, Mount Vernon Square, etc.

Toronto’s Avenues planning study can be found here, and the report’s executive summary is here. This kind of development is excellent infill and definitely worth pursuing for many cities (not just those with height constraints like DC). Still, the constraints are real and the opportunity for this kind of infill is limited, however promising it may be.

On Twitter, Neal Lamontagnetakes note of the positive abilities of regulations to shape urban development, and the need to balance against their costs:

[link] @ryanavent Agree, but – limits also linked to + land values. Still, not only economic but also design arguments. Better to shape than squish

Another comment from Payton, making note of the trade-offs in accommodating growth in other areas of the city:

In theory, it should be possible to significantly increase population and jobs within the District and not raise the existing heights. However, the city isn’t exactly littered with vacant lots; such increases would require a lot of demolition, and a lot of density within existing single-family neighborhoods.

Household sizes are *dramatically* smaller than they were: even though the city’s population dropped by 184,000 over the past 60 years, the number of housing units increased by 70,000. Much of that change came from carving up single-family houses into apartments, which is now much more controversial than it used to be.

Under the new Sustainable DC Vision, the city will need over 100,000 new housing units over just the next 20 years. Accommodating more households within the more location-efficient city will, as you know, reduce the region’s ecological footprint. But I genuinely wonder where these units can go: as I mentioned, due to the city’s small size there’s only 3-4 miles of redevelopable land along key arterials like Georgia, Rhode Island, and East Capitol — I’d add some in Upper NW, but you and I both know that’s highly unlikely — and those are only sufficient to address 10% of the total housing demand.

The real reason why Vancouver went whole hog for downtown skyscrapers was not about views, not about impressing people; it was about accommodating dramatic population growth while leaving its single-family neighborhoods mostly untouched, after a citizen revolt over “secondary suites” (accessory units). I know that my neighborhood is (mostly) ready for a few thousand more, perhaps even several thousand more, but is yours?

The point about feasibility is important. It just might be easier to go to Congress to change the height limit than it would be to fight a million NIMBY battles in established neighborhoods. There’s a case to be made for more of that type of development to be allowed by-right, but that too represents a big change.

Again to the last two commenters: how do you propose to add mid-rise density without demolishing huge swathes of low-rise buildings, either in the District or Arlington? Already, rowhouse neighborhoods like Chinatown, Foggy Bottom, Southwest/L’Enfant Plaza, the West End, and now Navy Yard and NoMa (particularly its eastern flank) have been sacrificed to extend the medium-rise downtown. Facadectomies are the only way that we have to remind ourselves that these were indeed low-rise at one point in time. Which neighborhoods should be demolished next for the growing downtown?

@tassojunior: we live in small enough apartments already — we have to, what with a median sales price of almost $500/square foot!

The problem is not with mid-rise densities, it’s with low-rise densities. I would be happy, perhaps even elated, to see mid-rise densities spread across a wide swathe of Washington, D.C., but I know that many others would not. Indeed, they, including many of Kaid’s neighbors in Ward 3, are already in open revolt, with dire consequences for the city, region, and planet.

You can’t squeeze a fast-growing balloon on the sides (protecting low-density neighborhoods) and the top (height limits) forever.

3 comments to Height limit trade-offs

Growth projections for the region are staggering. Those for DC, much less so. 800K+ housholds in next 30 years for the region, only about 100K+ for DC in the next 20. Given that we are adding about 12K units in the next few years, I don’t worry that much about the 100K.

And all those projections are incredibly straight line. Nature hates straight lines.

Even give that, we would be looking at a district of about 800-900K in 2040. Guess what — you’re still a small city! No BA, or Kyoto, or Paris. At best a San Jose or Austin.

Hah, I was about to compile these into my own post, except that I couldn’t even stop myself!

Anyhow, the MWCOG and OP growth projections aren’t actually straight lines. The trend, as you know, only recently turned around to population growth, and MWCOG projects a curve upwards as demand builds on itself. OP has raised its own goals and pulled the timeline up. As for where 100K units will come from, there are few blockbuster sites available at any price (potential for several thousand units, or a single federal agency, like Poplar Point and Pepco/Benning) and perhaps a few dozen sites for up to 1,000 units. As I tried to point out with the reference to the Avenues plan (and I’m trying to see if there are computed numbers on accessory units’ potential), incremental redevelopment doesn’t deliver huge numbers of units.

A few months ago, before really internalizing the growth figures, I had thought that DC could certainly grow only by altering existing zoning. Now, having witnessed a few more “victimless” NIMBY battles, my sympathy for the Height Act is diminishing.

How to Rebuild Architecture - NYTimes.com2014/12/17Architects are "attempting to sell the public buildings and neighborhoods they don’t particularly want, in a language they don’t understand. In the meantime, we’ve ceded the rest of the built environment to hacks, with sprawl and dreck rolling out all around us."